body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-image: url('素材.jpg');
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

.container {
    max-width: 600px;
    padding: 20px;
    background-color: rgba(255, 255, 255, 0.9);
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    text-align: center;
}

.game-board {
    display: grid;
    grid-template-columns: repeat(5, 100px);
    gap: 10px;
    margin: 20px;
}

.card {
    width: 100px;
    height: 140px;
    background-color: #d3d3d3;
    border-radius: 10px;
    cursor: pointer;
    transition: transform 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    color: black;
    position: relative;
    overflow: hidden;
}

.card::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, #4CAF50 0%, #81c784 100%);
    opacity: 0;
    transition: opacity 0.3s;
}

.card:hover::before {
    opacity: 0.5;
}

.timer {
    font-size: 24px;
    margin-top: 20px;
}

.game-over {
    margin-top: 20px;
    font-size: 24px;
    color: #4CAF50;
}

h1 {
    color: #333;
    margin-top: 0;
}